1. Field of the Invention
The present invention relates to a plasma process apparatus and a plasma process method for providing a film forming process at a temperature range of about room temperature using plasma with an object to be processed such as a semiconductor wafer.
2. Description of the Related Art
Ordinarily, when semiconductor integrated circuits are manufactured, semiconductor wafers undergo various processes such as a film forming process, an etching process, an oxidizing process, an diffusing process, a reforming process and a removing process of natural oxidation.
In recent years, it is required to process film forming materials at a low temperature in consideration of heat resistance or the like thereof. In order to deal with this requirement, there are proposed plasma process apparatuses using plasma with which reaction can be promoted even though a wafer temperature at a time of processing is low (Patent Documents 1 to 4).
An example of the plasma processing apparatuses is illustrated in FIG. 14. FIG. 14 is a schematic view of an example of conventional lateral-type plasma process apparatus. Referring to FIG. 14, semiconductor wafers W are held by a rotatable and multiple-stage wafer boat 4. The wafer boat 4 may be inserted or extracted into or from the processing container 2 by being moved up and down from a lower side of the processing container 2. Further, a lower end of the processing container 2 may be hermetically sealed by a lid 6. A plasma generating box 8 having a rectangular cross-sectional shape is provided in a sidewall of the processing container 2 along the height of the sidewall.
On both outer sides of the compartment walls of the plasma generating box 8, a pair of independent plasma electrodes 12 facing each other are provided along the height of the plasma generating box 8. A high frequency power of, for example 13.56 MHz, is supplied from a high frequency power source 14 for generating plasma to a region between the plasma electrodes 12. Further, an insulating material 16 is provided on the outer side of the processing container 2 including the outer side of a ceiling portion. Further, a heater 18 for heating the semiconductor wafer W is provided on the inner side surface of the inner side surface of the insulating material 16. A shield cover is provided on the outer side surfaces of the insulating material 16, and connected to ground to thereby prevent the high frequency from leaking outside.
In such a structure, when the high frequency power is supplied to the region between the plasma electrodes 12, plasma is generated. The gas supplied into the plasma generating box 8 is activated by the plasma to thereby generate active species. In this way, a reaction or the like is promoted by the generated active species even though the heating temperature is low.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2006-049809
[Patent Document 2] Japanese Unexamined Patent Publication No. 2006-270016
[Patent Document 3] Japanese Unexamined Patent Publication No. 2007-42823
[Patent Document 4] International Publication Pamphlet No. WO 2006/093136
In recent years, there is proposed a new technology called micro electro mechanical systems (MEMS) as assembling using a microfabrication technique. According to MEMS, a three-dimensional device such as a pressure sensor or a microphone may be installed in a small chip. One example of MEMS enables assembling a micromotor having a rotor. For example, when the micromotor is formed, a rotatable microscopic rotor should be formed. Therefore, a microscopic part corresponding to the rotor is previously formed to wrap an entire periphery of the microscopic with an oxide film. Then, a casing for accommodating the rotor is formed by a thin film. Thereafter, the entire oxide film is removed by etching it to thereby make an inside of the casing hollow. Thus, the microscopic rotor is furnished to have a structure in which the microscopic rotor is spontaneously rotatable inside the casing.
The thin film which is necessarily formed in mid-flow of the manufacturing process and removed later is referred to as a sacrificial layer which does not remain in the device. In a case of an oxide film, it is referred to as a sacrificial oxide layer. Film properties of the sacrificial layer and the sacrificial oxide layer are not a problem as long as the sacrificial layer and the sacrificial oxide layer are removed later. Therefore, when an oxide film or the like which is required to have good film properties such as ordinary gate oxide films and ordinary inter-layer insulating films, it is necessary to conduct a forming process under a relatively high temperature in order to acquire good film properties. Meanwhile, there is now being developed a technique of forming the sacrificial oxide layer under a low temperature region in order to form such the sacrificial oxide layer.
In order to form the sacrificial oxide layer, a plasma process apparatus as described with reference to FIG. 14 is used as a film forming apparatus. An aminosilane-based gas such as diisopropylaminosilane (DIPAS) and an active species such as ozone generated by plasma are used, and the sacrificial oxide layer is formed at a relatively low temperature of about room temperature.
However, when the plasma process apparatus as described with reference to FIG. 14 is used in order to form the sacrificial oxide layer, heat generated by plasma is accumulated in a space between the processing container 2 and the insulating material 16 at every batch process. As a result, when the batch processes are continuously conducted, there is a problem that a process temperature gradually increases at every batch process to thereby decrease reproducibility of forming the film.